Generally, CMOS devices have a P-type well and an N-type well formed in a substrate. Such semiconductor devices having two wells of different types are known as twin-well-type semiconductor devices.
In the prior art, with respect to twin-well-type semiconductor devices when the field oxide layer which was grown on an N-well region is removed after the P-well region on a silicon substrate is formed, problematically a step occurs on the surface of the silicon substrate, so that a characteristic of semiconductor devices might be deteriorated.
Therefore, it is an objective of the present invention to solve the problem set forth above and to provide a method for manufacturing a CMOS device having twin wells, which method can eliminate the step occurring on a silicon substrate.
The above-said objective should be construed as only one of many possible through the utilization of a few of the more practical and important features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objectives and a fuller understanding of the invention may be had by referring to both the summary of the invention and the detailed description, below, which describe the preferred embodiments and describe the scope of the invention defined by the claims, whose summary and description should be considered in conjunction with the accompanying drawings.